Klinefelter Syndrome

Klinefelter syndrome (also called Klinefelter's syndrome) is a genetic condition that affects 1 in 600 males. Boys with this condition are born with an extra chromosome, which affects some of their male characteristics. These include their fertility, libido and bone strength, which are reduced due to low testosterone levels, as an effect related to their genetic abnormality. However, most boys grow up and mature to become men with normal lives, without being aware of their condition.

What Is Klinefelter Syndrome?

Sex-related traits (your male or female characteristics) are determined by a pair of sex chromosomes that are found in the cells. Males have the X and Y (XY) chromosomes, while females have two X (XX) chromosomes. These, plus 22 other pairs of chromosomes, make up a total of 46 chromosomes that are found in every cell of the body.

Some males, however, are born with an extra sex chromosome (XXY), a condition called Klinefelter syndrome or XXY syndrome. The genetic abnormality, which was discovered in 1942 by Dr. H. F. Klinefelter, gives males a total of 47 chromosomes, resulting in low production of testosterone. This results in their male characteristics not developing fully, so babies are born with small testes, and boys having little facial hair and pubic hair during puberty. As adults, they are found to be infertile.

Some variations of this chromosomal abnormality include the mosaic Klinefelter syndrome, in which not all body cells have an extra chromosome, and rarely, a few males have extra copies of both sex chromosomes in their cells, which gives them a total of 48 XXYY, 48 XXXY, 49 XXXYY, or 49 XXXXY chromosomes.

What Are the Symptoms of Klinefelter Syndrome?

Many boys grow up with Klinefelter syndrome having few symptoms, while others may notice some effects on their growth or physical appearance. It may also be associated with problems in speech and learning in some boys. Symptoms may vary with age, and these include:


  • Undescended testicles
  • Weakness of muscles
  • Motor development slow
  • Delayed speaking ability
  • Quiet personality

Puberty and Young Adulthood

  • Taller than average
  • Long legs, short torso and broad hips
  • Puberty may be delayed, incomplete, or absent
  • After puberty, compared to others, they have less muscle, facial hair and body hair
  • Small penis
  • Small and firm testicles
  • Enlarged breasts
  • Weak bones
  • Low energy
  • Shyness
  • Problems in socializing or expressing feelings
  • Learning problems
  • Attention problems


  • Infertility
  • Small penis and testicles
  • Taller than average men
  • Reduced facial hair and body hair
  • Enlarged breasts
  • Weak bones
  • Low sex drive

When to See a Doctor

Consult a doctor to if you or your son has the following characteristics:

  • Slow physical development during childhood and puberty. Other symptoms include enlargement of breast tissue, small genitals, and firm testicles.
  • Delayed growth and development, including learning and speech problems, which can be treated early.
  • Infertility. If you are not able to father a child after a year of having regular and unprotected sex, consult a doctor.

What Are the Causes of Klinefelter Syndrome?

This genetic condition is not 'inherited' from parents. The random genetic error occurs during the process of cell division, where there is nondisjunction of chromosomes. However, it is possible that fathers or mothers who have babies at an older age have a greater likelihood of having a son with Klinefelter's syndrome.

What Are the Treatments for Klinefelter Syndrome?

If you have an XXY chromosomal pattern, no treatment can change it. However, there are a ways to treat your symptoms:

  • Education. XXY children may qualify for special educational services using certain classroom methods, such as breaking up big tasks into smaller steps.
  • Therapy options. Various therapists, including physical, occupational, speech, behavioral, mental, and family therapists, can help improve symptoms such as weak muscles, speech problems, and low self-esteem.
  • Medical treatment. Testosterone replacement therapy may be given to help increase your testosterone levels. This can help you develop bigger and stronger muscles, deepen your voice, and grow more facial and body hairs. This treatment may be started during puberty. Adults may also benefit from fertility treatments to help them have children.

How to Live With Klinefelter Syndrome

It is possible for XXY males to live a normal life with early treatment and support. Some boys grow up into mature men with minor symptoms. It is important to get not only medical treatment, but educational, as well as social support.


  • Monitor their development carefully. Seek help for speech, language, or other learning problems.
  • Encourage boys to participate in sports and other physical activities to help strengthen their muscles and improve motor skills.
  • Encourage them to be independent, instead of being overly protective. Provide a positive home environment with a lot of encouragement.
  • Cooperate with teachers, counselors and school administrators who can make a difference in your son's development.
  • Find available support, such as special services for education.
  • Connect with parents of boys with Klinefelter syndrome and join support groups to help ease your concerns and answer questions.


  • Consult a doctor for appropriate treatment to maintain physical and mental health and to prevent future problems, such as weak bones.
  • Consult health professionals who can help you with your options about planning a family.
  • Seek support from others who also have the condition. Find resources that provide more information about Klinefelter's syndrome and join a support group to learn more about how to cope with your condition.

Watch the video below to have a quick view on Klinefelter's syndrome:


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